1972 Float Adjustment ...

[Mark Maras]

 I agree. that's why the 1/16" (1.58 mm, 1 1/2 turns) below the nozzle top. It allows adjustment without fuel puddling on top of the nozzle.

[Stanley]

My  new fuel pump is putting out more fuel pressure than the old one and I want to see if it's affecting the float bowl levels. Will try the sightglasses first, then check by nozzle method. I'll use the magnifying glass for the nozzle method since I doubt if I'd be able to see fuel level in the nozzles well enough without it.

I don't want to complicate this topic since it's already sort of complicated but .... the drawing in the FSM shows that 23 mm measured from the underside of the middle of the  lid, not at the rim of the lid. There's no easy way to measure from the underside of the lid. Others have measured from the underside of the lid to the edge as 3 mm, so that makes it 20 mm down from the edge disregarding front / rear difference. We all assume the drawing is correct. But how do we know that ?  Maybe the 23 mm was supposed to be measured from the edge and the engineer that drew it got it wrong. I trust the FSM but not 100%, especially a oddball measurement like that. Sorry in advance. 

[Mark Maras]

 I think we're all hoping for some clarity on this. Thanks in advance. 

[Captain Obvious]

11 hours ago, Stanley said:

We all assume the drawing is correct. But how do we know that ?  Maybe the 23 mm was supposed to be measured from the edge and the engineer that drew it got it wrong.

I've been thinking the same thing. It's very "un-Datsun" like for them to give a spec that is actually unusable and unmeasureable in reality. I've been thinking there may have simply been a dimensioning mistake there. I mean, it's clear that the documentation is not without error... For example, on that very same page (EF-25 of 72 manual), they say "dimension "H" in Figure EF-46" while it's clear that's a typo and they actually meant "Figure EF-47".

So I take that "inside of the lid" dimension with a grain of salt, but without factory confirmation (which will never happen), it's all we got.

When I set my floats, I accounted for about two mm for the gasket and the thickness of the lid casting and set mine at 25 mm down from the OUTSIDE TOP of the bowl lid. My car ran great. YMMV.

Contrary to a lot of the discussion between you guys above, my experience is that the float bowl level is not that super critical to the overall operation of the carbs. 23 mm down, 25 mm down... Didn't seem to make that much difference to me on a stock engine. Of course, I had gone over the rest of the carbs and everything else and was confident that everything was working as intended. If that's not the case, you end up chasing your tail.

No short cuts. You either have the skills to do it yourself, or if not, you take it to someone else who does. Or you sell the car and buy something more mainstream. Something that has a local following of experts in your area.

[siteunseen]

That's what I think too Captain.  Close is good enough then fine tune them with the nozzles or "equally crappy" as 240260280 says. 

Getting the choke cables right was harder for me than the floats.

[Mark Maras]

31 minutes ago, Captain Obvious said:

 

Contrary to a lot of the discussion between you guys above, my experience is that the float bowl level is not that super critical to the overall operation of the carbs. 23 mm down, 25 mm down... Didn't seem to make that much difference to me on a stock engine. Of course, I had gone over the rest of the carbs and everything else and was confident that everything was working as intended. If that's not the case, you end up chasing your tail.

 

 I've been considering this possibility and It could be that minor variations in the fuel height don't make much difference. It could be that this float level discussion is "much ado about nothing." Then I thought about a lower fuel level and how it would affect the choke. Pulling the choke on will have less effect if the fuel level is low. Dropping the nozzles and allowing fuel to puddle on top of the nozzles is the choke action. It would probably only affect cold starting if the fuel level was low and the temps were frigid. Like trying to start your Z in the garage in the dead of winter.

[siteunseen]

Mine ran pretty good as long as I was on flat land. 

That was when they only were getting about a quarter full.  When I went up a steep hill the front carb would shut down.

It's hard to for me to think it's just the carbs after ztherapy sent him a good set and all his problems started.

I think Black Gold Man had the best idea, go to that race track and find a Datsun mechanic from a local race team.  They should have the phone number or a name at least on their trailers.  Get some binoculars and sit in the parking lot, write down all you can see

[Captain Obvious]

Actually I believe the choke action has little to do with the fuel level, but is all about the larger gap between the needle and the nozzle. When you drop the nozzle, what you are effectively doing is pulling the needle out of the nozzle and enlarging the jet size to richer the mixture.

Larger jet, more fuel.

[jalexquijano]

Track?? There is no reliable datsun mechanic here. I am following Mark's advice to set the floats at 2.5 turns 1/16 inch.  Just remember my car has been overhauled to 2.6 liters and has a schneider 274f camshaft. Its not stock.

[siteunseen]

I know if I leave my choke lever pulled back overnight the bowls empty until the level gets even with the nozzle's top.  With my water heater down there it didn't take too long to break that carelessness. 

[Mark Maras]

@jalexquijano Where are your mixture screws now and how is it running?

[siteunseen]

22 hours ago, Mark Maras said:

@jalexquijano Where are your mixture screws now and how is it running?

5 months left, tick tock!